As a toner fixing device for use in an image forming apparatus such as a copy machine and a printer, a device using a fixing method of heating unfixed toner while moving a recording paper after forming a toner image to be held on the recording paper corresponding to image information by an electrophotographic operating process is generally used.
The fixing device fuses the toner (made of a resin material, a magnetic material, and a colorant) by moving the recording paper and the toner held on the recording paper by static electricity while sandwiching the recording paper and the toner between fixing means composed of a roller that conveys the recording paper and the toner while rotating, and pressurizing means composed of a roller that rotates in an opposite direction from the fixing means in press contact therewith and applying heat and pressure thereto, and thereby fixes the toner onto the recording paper.
A temperature of the roller greatly affects an image quality. Thus, the temperature of the roller is controlled by detecting a temperature of a roller surface by using a sensor.
There is known an infrared temperature sensor which detects the temperature of the roller in a non-contact manner so as to avoid damage to the roller of the fixing device (e.g., Patent Literatures 1 and 2). The infrared temperature sensor includes an infrared detection element and a temperature compensation element, so that the infrared detection element detects a heat emission amount of infrared rays from the roller as the fixing means that is an object to be detected, and the temperature compensation element further detects an atmosphere temperature to perform temperature compensation, thereby specifying the temperature of the object to be detected.